1. Field of the Invention
The present invention relates to integrated circuits, and more particularly to an output buffer circuit.
2. Description of the Related Art
A data output circuit, or an output buffer circuit, for driving an external load of a large capacitance, is used as a circuit for outputting the data generated in a semiconductor integrated circuit (referred to as an IC) to exterior.
The output buffer circuit is generally provided with an input node and an output node, and output transistors that are conductive in response to a signal applied to the input node. The load capacitor connected to the output node is charged or discharged to a power source voltage through the conducting output transistors. Such output transistors have an extremely large current drive ability to charge or discharge in a short time the load capacitor of a large amount for example, 100 pF.
The power source voltage and the ground voltage are supplied through wires to the IC in a package. When the output transistors charge or discharge the load capacitor, a large current flows through the wires. The large rate of change in drive current can induce a large voltage drop across the inductances of the wires and the package. The resulting noise in the internal power source voltage and the ground voltage causes an erroneous operation of the IC.